A diagnostic, therapeutic, or other interventional procedure on a human or animal subject may involve introducing an instrument toward a desired target location within the subject. For example, an interventional procedure on the subject's brain may involve drilling a burr hole in a subject's skull, mounting a trajectory guide on the subject's skull, and guiding an instrument (e.g., a catheter, a needle, a cannula, an electrode, or other device) to the desired target within the subject, such as by using pre-operative or live images from an imaging modality (e.g., MR, CT, PET, ultrasound, etc.) in an image-guided procedure. Accurate guidance is desirable, particularly for an interventional procedure on the brain, where millimeter or sub-millimeter accuracy of the instrument location may be desirable. Some illustrative examples of interventional procedures on the brain can include, but are not limited to, deep brain stimulation (DBS), infusate delivery (e.g., of a pharmaceutical, biological, or other substance), or microelectrode recording.
Ferrara U.S. Pat. No. 4,809,694 discloses a raised ball-and-socket trajectory guide, in which a deformable ball is located substantially above the burr hole of the skull. In Ferrara, an external thumbscrew can be used to deform the ball to retain an instrument within a ball passage through the deformable ball.
Parmer et al. U.S. Pat. No. 6,902,569 discloses a ball-and-socket trajectory guide with a split ball providing hemispherical sections that capture a relaxable stabilizer. When a guide stem is removed from the ball, the relaxable stabilizer relaxes to grip an instrument within a ball passage through the relaxable stabilizer. After adjusting the instrument trajectory by pivoting the ball, the ball is locked into position using a hexagonal-handled locking member (230) (see Parmer at FIG. 7A that protrudes substantially above the burr hole and the skull). The instrument is then inserted through the locked-in trajectory. The protruding hexagonal-handled locking member (230) is then removed, and a cap 310 is pressed or threaded into place to cover the ball. (See Parmer at col. 14, lines 22-38.)
Skakoon U.S. Pat. No. 7,204,840 and Skakoon U.S. Pat. No. 7,815,861 disclose examples of ball-and-socket trajectory guides that can be used in conjunction with peel-away sheaths. Skakoon U.S. Pat. No. 7,204,840 also shows an example of fiducial markers that can be attached to component associated with a trajectory guide apparatus. (See Skakoon U.S. Pat. No. 7,204,840 at FIG. 39.)
Jenkins U.S. Patent Publication No. 2007/0171184 discloses an example of a raised saddle trajectory guide that can be used in conjunction with a peel-away sheath. (See, e.g., Jenkins at FIG. 6c, ¶0067, ¶0073, ¶0076.)